1. Technical Field
This invention relates to an improved method of producing a gasket for a building cladding, curtain wall or glazing system, and to the gasket so made.
2. Description of the Prior Art
The term ‘gasket’ refers to the rubber or other plastics material extrusions used to hold or seal an infill into a framework or the like in a curtain walling/glazing system in the construction of buildings.
In our published UK patent specification number 2 023 703 and our European patent publication number 0 059 058 building systems are described in which infill members are held in place on a framework by means of a flexible gasket which locates and is gripped by the framework and has a limb extending so as to bear against the infill and hold it in place. This system is very successful and is used extensively. A particular feature of it, which appeals to architects, is that the gasket can be of various colours, or indeed multi-coloured, to produce a desired aesthetic effect.
One problem area in connection with the gaskets of the above systems is in connection with the gasket corners. Reference to FIGS. 1 and 2 of the accompanying drawings illustrates the current method of producing corners. The main runs of the gasket are extruded to the desired length. Two extrusions 10 are inserted into a mould 12 and a shot of silicone compound is inserted under pressure into the heated mould forming a joint 14 between the two extrusions. Because the moulding is carried out under pressure, it is easy for protruding lines 16 to appear on the resultant product, which are not aesthetically pleasing. Similarly, because the corner is injected rather than extruded, there is very often a colour differential and a different surface finish between the corner 14 and the extrusions 10. In addition, the corner needs to be radiused at 18 to ensure weather-tightness when a clean right angle may be preferred aesthetically. Finally, it is only possible to use a single solid colour whereas the extrusions can be produced in multiple colours or with metallic pigments.
The invention seeks to provide a method of forming a gasket joint, e.g. corner, improved in the above respects.
According to the present invention there is provided a method of forming a joint between two plastics extrusions which comprises mitring the extrusions so that they form the desired angle to one another, removing part of the rear face of each extrusion, placing the mitred extrusions in a mould and injecting a resin material whereby to bond the extrusions to one another and produce the desired joint configuration.
Because the front surface of the joint in accordance with the invention is entirely made up from the original extrusion, there are no problems with raised sight-lines, colour differentials, surface differences, or colour matching. Moreover, the method of the invention allows a corner to be produced which has a clean right angled rather than radiused inner portion.
The extrusions will be made from a suitable plastics materials, e.g. as described in the above mentioned patent publications. Currently it is preferred that the extrusions are made from a silicone rubber, although other plastics materials may be used. Accordingly the resin used to form the joint is normally also a silicone rubber mix which will cure under heat and pressure in order to produce the joint, although other compatible plastics materials can be used. Also, although the invention is especially useful when used with the extrusions of our above referred to patent publications, it has wider applications and can be used to join plastics extrusions in the curtain wall/glazing field generally, wherever it is desired to maintain the surface appearance of an extrusion through the joint or corner.
The invention further includes a gaskets having joints formed in accordance with the above.